Colin Millar writes:
 > I am having trouble reading in a record of real numbers from an ascii file
 > to a real array of fixed maximum size.

 > I do not fully
 > understand the limitations / benefits of using list directed input to read
 > ascii files.  Is it that the list directed input only completes when each
 > array element has had data read into it?  Or if the no. of entries in the
 > file record and the size of the array do not match, then does that
 > constitute an input conversion error??

That doesn't constitute a conversion error, but its consequences might.
I think the critical piece you are missing is that list-directed input
is *NOT* restricted to reading a single record.  If you tell it
to read an array of, say, 100 elements, then list-directed imput
will continue until it reads 100 values, or until it hits the end
of file (in which case you will get an end-of-file condition),
or until it hits a "/" character.

What is probably happening to you is that, not finding enough values
on the first record, the list-directed read is continuing to
subsequent records where it finds data that doesn't look like
reals.  (Or perhaps it finds some records of appropriate-looking
data, but has in the process used up records that you expected
to read with later statements, throwing them off).

Solutions include

1. If you can manage to put a "/" (without the quotes) after
   the qbasic-written data, then the read will do exactly
   what you want.  You could even put the "/" on a separate
   line as long as you never actually have enough data to
   fill the array.  (If you have enough data, then the read
   will stop without going on to the "/" line).

2. You could read the whole line into a character variable
   using an "A" format.  Then do an internal read from that
   character variable using list-directed.  (This is an f90
   list, so I assume you are using an f90 compiler.  Internal
   list-directed I/O is non-standard in f77, but is standard
   in f90).

   You'll then get an end-of-file condition when the read hits
   the end of the character variable (so be sure to use an
   appropriate end= or iostat=).

Note that none of the above solutions will directly tell you how many
elements were read.  You might be able to tell that by pre-filling
the array with some value known to be invalid (assuming that you
can come up with such a value).

--
Richard Maine                |  Good judgment comes from experience;
[log in to unmask]   |  experience comes from bad judgment.
                             |        -- Mark Twain